An above-room-temperature phosphonium-based molecular ferroelectric perovskite, [(CH₃)₄P]CdCl₃, with Sb³⁺-doped luminescence

Molecular ferroelectrics are attracting tremendous interest because of their low cost, mechanical flexibility, easy processing, low weight, and low acoustical impedance. Moreover, their combination of ferroelectric and optical properties has led to investigations of their many potential applications, such as low-energy electron excitation and field emission displays. However, luminescent molecular ferroelectrics have rarely been reported, except for several AMnX₃-type or lanthanide ion-based luminescent ferroelectrics. Here, we report the first above-room-temperature phosphonium-based molecular ferroelectric perovskite, [(CH₃)₄P]CdCl₃ (1), with a high Curie temperature (T_c = 348 K) and moderate remanent polarization (P_r = 0.43 μC/cm²). Using piezoresponse force microscopy (PFM), the typical stripe-like domains of ferroelectrics can be observed. Moreover, 1 exhibits orange luminescence under UV excitation after doping with Sb³⁺, which represents a first step toward realizing luminescence-enhanced molecular ferroelectrics with various wavelengths. These results will inspire the further exploration of phosphonium-based ferroelectrics and pave the way toward practical applications in ferroelectric luminescence and/or multifunctional devices.